Abnormal gonadotropin release and carbohydrate metabolism in morbid obese women

Obese women are associated with clinical symptoms suggestive of abnormal reproductive functions including irregular menses and infertility. Previous studies of gonadotropin release in obese women, basal or after luteal hormone releasing hormone (LHRH) stimulation, are controversial. Obese women are also often characterized by glucose intolerance and hyperinsulinemia which might relate to their excessive body fat. To understand the link between abnormal gonadotropin release, carbohydrate metabolism and percent body fat, we examined 17 premenopausal morbid obese women with body mass index (BMI) 38.7 +/- 1.6 Kg/m2 (mean +/- SEM) and 16 age-matched lean controls with BMI 19.7 +/- 0.6 Kg/m2. Plasma glucose, insulin and C-peptide values were measured before and 30, 60, 90 and 120 min after a 75 gm oral glucose tolerant test (OGTT). Each individual also received LHRH test which involved determinations of serum LH and FSH values at basal, 15, 30 and 60 min after injection of LHRH for 0.1 mg intravenously. Women with morbid obesity had significantly greater responses of glucose, insulin and C-peptide values as compared with lean women (all p < 0.001, two-way ANOVA). Despite that basal concentrations were not different, serum LH, FSH and ratio of LH to FSH values in response to LHRH test showed significantly lesser increase in obese women than lean controls. Percent body fat, determined by bioelectrical impedance analysis, correlated positively with plasma glucose, insulin and C-peptide responses to OGTT while negatively with ratio of LH to FSH responses (r = -0.418, p < 0.01) to LHRH test. Body mass index also correlated inversely with ratio of LH to FSH responses (r = -0.472, p < 0.01). In conclusion, morbid obese women had glucose intolerance, hyperinsulinemia and lower responses of serum LH and FSH values as compared with lean women. Excessive body fat play an important role in mediating these carbohydrate and gonadotropin abnormalities.